Green River Plant Fossil – Eocene Green River Formation, Bonanza, Utah, USA

Authentic Green River Plant Fossil – Eocene Epoch, Bonanza, Utah, USA

This exceptional Green River Plant Fossil originates from the world-renowned Green River Formation in Bonanza, Utah, USA, and dates to the Eocene Epoch, approximately 50 million years ago. This genuine specimen preserves the delicate remains of ancient plant life that once thrived along the shores of vast subtropical lakes, capturing a moment in time from one of the most important fossil-bearing formations in the world.

Every specimen we offer is 100% genuine and comes complete with a Certificate of Authenticity. The photograph shows the exact specimen you will receive, displayed with a 1 cm scale cube for accurate size reference—please see the photo for full sizing details. This particular fossil has been carefully chosen for its definition and preservation quality, revealing exquisite detail of leaf or stem structure from ancient Eocene vegetation.

Geological and Depositional Environment

The Green River Formation spans parts of Utah, Wyoming, and Colorado and represents one of the most extensive and scientifically significant Eocene lacustrine (lake) deposits on Earth. These sediments were laid down in a series of vast freshwater lakes, including Fossil Lake, Lake Uinta, and Lake Gosiute, which existed approximately 53 to 48 million years ago.

In the Bonanza region of Utah, the Green River Formation primarily consists of calcareous shales, mudstones, and fine-grained limestones, which accumulated under calm, oxygen-poor lake conditions. These fine sediments allowed for exceptional fossil preservation, often encapsulating plants, fish, insects, and even small vertebrates with remarkable fidelity. The low-oxygen environment inhibited decay, allowing delicate organic materials such as leaves and stems to be preserved as thin carbon films or impressions.

The fossils from Bonanza are notable for their light brown to dark grey matrix and finely detailed organic impressions. Each plant fossil tells a story of the Eocene greenhouse world, when the global climate was warmer and more humid, and lush subtropical forests extended far beyond their modern ranges.

Paleobotanical and Scientific Significance

Plant fossils from the Green River Formation are key to reconstructing the ancient ecosystems and climates of North America during the Eocene. The flora of this formation includes a diverse array of species—ferns, palms, willows, sycamores, poplars, and other flowering plants—reflecting a richly vegetated environment surrounding the ancient lakes.

This particular specimen captures the morphology and venation of Eocene plant life, preserving fine details that help palaeobotanists identify leaf families and infer their growth conditions. Many specimens display visible midribs and secondary veins, providing insight into photosynthetic adaptations in a world undergoing major evolutionary change following the extinction of the dinosaurs.

The fossilisation process transformed organic matter into a carbonised impression on shale, retaining the original shape and pattern of the leaf or stem. Such fossils are critical to understanding the evolution of angiosperms (flowering plants) and the transition of vegetation across ancient climate gradients.

Geological Stage and Age

• Formation: Green River Formation

• Age: Eocene Epoch (~50 million years old)

• Stage: Lutetian to Ypresian

• Environment: Freshwater lacustrine, low-oxygen sedimentation

• Locality: Bonanza, Uinta Basin, Utah, USA

The Green River Formation represents one of the most complete continuous sedimentary records of the Eocene, capturing tens of millions of years of biological and geological history. Its strata record seasonal fluctuations in water chemistry, volcanic ash deposits, and organic-rich laminae—each thin layer documenting a year of deposition in these ancient lakes.

Collectable and Display Qualities

This Green River Plant Fossil combines scientific importance with natural beauty. The fossil’s delicate organic pattern contrasts beautifully against its fine-grained matrix, making it an ideal display piece for collectors, educators, or enthusiasts of natural history. Its authenticity, provenance, and clear preservation make it suitable for both private collections and academic study.

Each specimen serves as a direct connection to the deep past—a tangible fragment of the lush forests that covered the ancient landscapes of Eocene North America. Its aesthetic and scientific value make it a prized addition to any geological or palaeontological collection.

Authenticity and Presentation

All of our fossils are 100% genuine specimens, professionally verified and supplied with a Certificate of Authenticity. The photograph shows the exact fossil you will receive, alongside a 1 cm scale cube for accurate measurement.

This beautiful Green River Plant Fossil from Bonanza, Utah captures an extraordinary piece of the Earth’s prehistoric flora—preserved for over 50 million years within the ancient sediments of the Green River Formation, a true window into the warm, verdant world of the Eocene.